How much of “Doctor Who” might really be possible?

Science shows why Doctor Who is so special.

As Doctor Who’s 50th anniversary looms, time travel is everywhere – on the screen, at least. Famously, the Doctor can whizz through the years using a “dimensionally transcendental” machine, the TARDIS, and make changes to the past as and when he likes. But what is time travel – and how much of “Doctor Who” might really be possible?

A handy definition of time travel comes from philosopher David Lewis. Lewis says time travel involves a journey having different durations viewed from outside (in “external time”) or from inside (in “personal time”). Suppose you spend five minutes travelling aboard your machine, as measured by (e.g.) your watch and your memories. On arrival, you find 150 years have elapsed in the outside world. Congratulations, you have time-travelled. Five minutes of your personal time has covered 150 years of external time.

Odd as this sounds, Einstein’s theory of Special Relativity introduced such possibilities to physics in 1905. The theory says: the duration of a process varies with the relative velocity of the observer. The closer that relative velocity gets to the speed of light, the longer the travelling process takes.

Suppose you want to see the Earth a billion years hence, but worry you have only about 50 personal years left. Special Relativity specifies that if you travel very close to the speed of light relative to the Earth, your 50 personal years can cover one billion Earth years.

In backward time travel, personal and external time differ in direction, so journeys end in external time before, not after, they begin; you spend five personal minutes travelling 150 years into the external past. General Relativity suggests that the universe is essentially curved spacetime, which might allow such divergences of external and personal time.

Relativity treats space and time as aspects of a single entity: “spacetime”. One of the more remarkable features of General Relativity is that it allows time and space axes to be interchanged, so one observer’s space axis can be another observer’s time axis.

In 1949, Austrian mathematician Kurt Gödel used General Relativity to describe a universe where intrepid voyagers can go anywhere in (past or future) time without travelling faster than light. Gödel’s universe has no boundaries in space or time, and all the matter in it rotates. But our finite, non-rotating universe is not Gödel’s. Despair not though – simply spin an ultradense, very (maybe infinitely) long cylinder very fast. Spacetime should curve around the cylinder so the direction of the local future partially points into the external past. Such devices are called “Tipler Cylinders”, after physicist Frank Tipler.

Better yet, quantum theory suggests that “wormhole” connections between different spacetime points spontaneously form and break all the time. The chances are that natural wormholes are tiny - vastly smaller even than an electron, (and a billion trillion electrons can fit in a teaspoon). But you could perhaps find (or create) a wormhole big enough and durable enough to let you slip through into the past. Difficult, but theoretically possible.

No, you can’t kill your physics teacher

So perhaps you could travel into the past. But what about paradoxes? What is to stop you assassinating your grandfather or yourself as infants? One answer says: logical consistency.

Classical logic says you cannot consistently kill in infancy someone who achieves adulthood. But, Lewis says, time travel need not involve doing the logically impossible – provided travellers’ actions in the past are consistent with the history whence they come. So you could try killing your baby grandfather, but something would foil you – you would sneeze, or your gun would jam. Lewisian time travel is therefore (classically) consistent, but might look very strange, since seemingly possible actions (like shooting an unprotected infant) would prove impossible.

Another view says that backward time travel requires many worlds – that is, many different but equally real versions of physical reality. Physicist David Deutsch and philosopher Michael Lockwood argue that time travel must involve inter-world travel. If you travel backwards in time, you must arrive in a history different from your native one and so would be quite unfettered by your past once you get there. You could even kill this other history’s counterparts of your grandfather and yourself.

Both these concepts of backwards time travel may disappoint anyone wanting to change the “one and only” past. Conventional logic says time travellers would either help make history what it was (Lewis) or create a different history (Deutsch/Lockwood). However, quantum logic might let travellers change the actual (one-and-only) past.

Suppose we hold that quantum measurements determine (or change) quantities measured, even if those quantities lie in the past. Someone could travel back and “observe” history turning out differently from how it originally was, thereby retrospectively making actuality different from what it had been. What would happen to travellers who rebooted history is not clear, but this model seems closer to the time travel familiar from “Doctor Who” and other fictions. Beware, though, because quantum theory allows no predicting, and still less controlling, of the outcomes of changing the past. There would be no way to foresee the effect you would have on the present.

So classical logic, General Relativity and quantum theory all seem to permit time travel. Classical logic plus General Relativity suggest backward travellers face weird consistency constraints. Many-worlds travellers face no constraints, but get displaced into different histories. Quantum-logic travellers could change the (one and only) past without constraints, but they couldn’t predict or control what they would get.

So far, however, it seems only the Doctor knows how to change the past at will.

Alasdair Richmond received funding from the Arts and Humanities Research Council, to fund one semester of a two-semester leave period that covered the academic year 2008-2009.

The Conversation

This article was originally published at The Conversation. Read the original article.

The eleven incarnations of the Doctor. Image: BBC/Matt Burlem

Alasdair Richmond is a Senior Lecturer in Philosophy at the University of Edinburgh.

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Beautiful and the damned: a spellbinding oral history of Hollywood

West of Eden: An American Place by Jean Stein follows a specific tribe of people: the beautiful.

One day in LA, the showbiz tycoon David Geffen drove by the house that had belonged to Jack Warner, the co-founder of Warner Brothers. The gates were open, so he went in. “It was so grand and so Hollywood . . . It was an homage to an idea about the way people lived in Hollywood. I got caught up in the whole gestalt and I bought it.” Geffen then marvels that he paid $47m for the homage, while Jack had sold his whole studio for just $38m in 1956. You have to have a sense of irony.

From around 1920 there was a tribe in southern California, sometimes known as “the beautiful people”. In many cases, they were technical beauties (they appeared in dreamlets known as movies or had their photographs in magazines made of heavy, perfumed pages). Yet the true beauty talked about was a spiritual aspiration – a quest for romantic nobility, fragile elegance, or serene madness – that might offset the inner derangement, selfishness and comic vulgarity that so threatened their longing for godless class, or inscrutability. They lived within the frantic church known as Hollywood, a fierce cult or early form of terrorism (it hired intimidators, all of them called Oscar) that cherished the hopeless grail of beauty and sacrificed many lives in its pursuit.

Jean Stein is one of them; she admits as much in West of Eden, which seems to me the best book ever done on the terrifying social dysfunction of the beautiful people. Ms Stein is now 81. She is the daughter of Dr Jules Stein (1896-1981), the son of Lithuanian Jews, who became a celebrity ophthalmologist yet so loved music and show business that he founded the MCA agency – Music Corporation of America.

The marriage of medicine and ten-percenting is important to this book, and Jean Stein – who is clear-eyed, and knows where the bodies are buried – has the innate touch and scalpel smile of an expert autopsist. She does not quite write, but she composes absorbing, novelistic oral histories. In 1982 she did one on Edie Sedgwick, the Sixties model, junkie, sexpot and icon, a ghost long before her death. Now Stein delivers a calm Götterdämmerung that can be read as the fearsome annals of a haunted Hollywood, as well as an adroit response to John Steinbeck’s East of Eden (1952), earlier proof of California’s soft spot for fallen angels.

West of Eden is selective and yet, by the end of its 334 pages, you feel that the light and the shadow have fallen on nearly every­one. There are just five subjects. First: Edward L Doheny, the oil tycoon who established the architecture of Los Angeles, and helped inspire There Will Be Blood. Then there are the Warners, but chiefly Jack, the youngest of four who outlived and betrayed his brothers, and who abandoned a nice Jewish wife for an adventuress and ended up being painted by Salvador Dalí and dreaded as “a character”. There is also Jane Garland, a schizophrenic child of great wealth who drifted around with various unofficial nurses and uncertain friends. Next is the teeming casebook called Jennifer Jones; and then the Steins themselves, which means Jules and Jean, and her two daughters by William vanden Heuvel, one of whom now publishes the weekly magazine the Nation.

In shaping these five windows, Stein has interviewed numerous tribe members, many of whom have memories, wounds and nightmares for which they are in therapy (or script development – the two forms are very alike). Her tone and manner are matter-of-fact, but she knows how wary those close to Eden are about trusting stories. Life is a competing set of fantasies, and given that lies have always been allowed in LA, falsehood itself, as a moral handicap, has come to mean little. Though all “true”, this book reads like a dream.

A short review cannot cover all five windows in detail, so let me fix on the one I know best: the glass or screen in which Jennifer Jones existed like a butterfly. Born in 1919 (Gore Vidal once told me she was three years older; gossip devours fact), she was the daughter of an Oklahoma showman who thought she would act – on screen, of course, but also always and everywhere. She married a young actor, Robert Walker, and they had two sons. Then in 1941 she was seen by the mogul David Selznick: he was moved by her and she was drawn upwards by her chance of stardom. Each abandoned a spouse and two sons. They became archetypes of misjudgement, though her mediocre acting never matched the skill or glow of other Selznick employees (such as Ingrid Bergman). They had a daughter, Mary Jennifer, who lived in rivalry with her mother and loathed her, and finally killed herself.

Jennifer, as Lauren Bacall reports, could be a little nutty. She and Selznick gave lavish Sunday parties: “Jennifer was busy doing her make-up and combing her hair and changing her outfit. She was kind of playing her part. She was always trying to be noticed, to have people really care about her and be there for her.”

This is not pretty stuff; maybe that is why these people were so desperate to be beautiful. Indulgence and neglect formed a damaging mixture that left bodies lining the roadside west of Eden. Lawyers and doctors catered to the stricken beauties. Shrinks played an especially devious role, though “shrink” was the wrong word; those hired to soothe mania in fact inflated their clients’ egos and dramatised their self-pity, the movie in which we all take part.

Hard to credit, often hard to stomach, this is a spellbinding record of that ancien régime. Whatever happened to the tribe? The members may be thinner on the ground now in southern California, but their ignoble nobility is everywhere.

David Thomson’s books include “Showman: the Life of David O Selznick” (André Deutsch) and “How to Watch a Movie” (Profile Books)

West of Eden: An American Place by Jean Stein is published by Jonathan Cape (334pp, £20)

This article first appeared in the 05 February 2015 issue of the New Statesman, Putin's war